Facilitating bi-directional extracellular electron transfer via the n-type conducting polymer poly(benzodifurandione).

Shewanella oneidensis MR-1 is a model electroactive bacterium capable of bidirectional extracellular electron transfer (EET), though inward EET remains energetically challenging due to the low potential required for intracellular reduction. Here, we report the use of poly(benzodifurandione) (PBFDO), an n-type conducting polymer, as an electrode modifier to enhance both outward and inward EET in S. oneidensis MR-1. The PBFDO-modified electrode exhibited improved biofilm morphology and cell viability compared to fluorine-doped tin oxide (FTO), as confirmed by microscopy. Electrochemical measurements revealed that PBFDO significantly enhanced EET performance, showing higher current densities and more pronounced redox features. Notably, the impedance at low frequency decreased from ∼295 kΩ (FTO) to ∼7.8 kΩ (PBFDO), indicating substantially improved interfacial electrochemical performance. These results demonstrate that PBFDO provides an effective low-potential, biocompatible interface for bidirectional EET, highlighting the potential of n-type polymers to enable efficient electron injection for bioelectrosynthesis applications.